* Epithelial Tissue Types Are Named by Their Shape and Number of Layers

EBTISAM AL BUTTI/171/2004

* Epithelial tissue always has a free surface. Cells are close together and attached to basement membrane.

* Epithelial tissue types are named by their shape and number of layers.

Locations:

·  Surface of the body

·  Covering and lining most organ

·  Secretory Glands

·  Sensory area of sense organ.

Functions of Epithelial Tissue

·  Protection

·  Sensation

·  Secretion

·  Absorption

·  Excretion

·  Diffusion

·  Cleaning

·  Reduces Friction

Layer Designations

Simple

/

One layer of cells

Stratified /

More than one layer of cells

Pseudostratified / One layer of cells that appears to be many layers.
Cell Shapes

Squamous

/

Flat cells

Cuboidal / Cube shaped cells
Columnar / Column shaped cells, tall and skinny
Simple Squamous / Found in the alveoli of the lungs, lines blood vessels. One layer of flat cells permits filtration and diffusion.
Stratified Squamous / Found in the skin, esophagus and vagina. The many layers of cells offer protection of these areas.
Simple Cuboidal / One layer of cube shaped cells. Simple cuboidal lines the kidney tubules. It's function is secretion and absorption.
Stratified Cuboidal / Many layers of cube shaped cells. Stratified cuboidal lines the mammary glands and salivary glands. Like stratified squamous, it's function is to offer protection of the areas it lines.
Simple Columnar / 2 types: ciliated and non-ciliated. Non-ciliated the GIT. You will also find goblet cells here (which secrete mucus). Ciliated simple columnar lines the fallopian tubes, and the cilia beat to move the oocyte through the tube.
Stratified Columnar / Like other stratified epithelial types, it's function is to protect. Also secretion. Rarest epithelial type.
Pseudostratified Columnar / Lines the Upper Respiratory Tract where it functions to produce and move mucus. (Has cilia and goblet cells).

Simple Squamous Epithelium

Description:

·  Single layer of flat cells

Locations:

·  Lining of ventral body cavities

·  Lining of heart and blood vessels

·  Portions of kidney tubules

·  Inner lining of cornea

·  Gas exchange surfaces in lungs

Functions:

·  Decrease friction

·  Controls vessel permeability

·  Absorption

·  Secretion

Simple Cuboidal Epithelium

Description:

·  Single layer of cube-shaped cells

Locations:

·  Glands

·  Ducts

·  Portions of kidney tubules

·  Thyroid gland

Functions:

·  Limited protection

·  Absorption

·  Secretion

Simple Columnar Epithelium

Click here for pictures

Description:

·  Single layer of cells that are taller than they are wide

Locations:

·  Lining of stomach

·  Lining of intestine

·  Lining of gall bladder

·  Lining of Fallopian tubes

·  Lining of collecting ducts in kidneys

Functions:

·  Protection

·  Absorption

·  Secretion

Simple columnar epithelium / Ciliated columnar epithelium

Pseudostratified Columnar Epithelium

Description:

·  Appear stratified

·  Nuclei of cells at different levels

·  All cells contact basement membrane

Locations:

·  Lining of nasal passages

·  Lining of bronchi

·  Lining of trachea

Functions:

·  Protection

·  Secretion

Goblet cell

Glandular epithelium

Stratified Squamous Epithelium

Click here for pictures

Description:

·  Several layers of cells

·  Cells at surface are flat

·  Cells near basement membrane are cuboidal

Locations:

·  Surface of skin

·  Lining of mouth, throat, rectum, anus, vagina

Functions:

·  Provides physical protection against abrasion, pathogens, and chemical attack

Stratified Columnar

Description: Several layers of polyhedral cells; columnar cells only in superficial layer.

Location: Lines part of male urethra, large excretory ducts of some glands, and small areas in anal mucous membrane.

Function: Protection and secretion.

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